Devices and methods for removal of acute blockages from blood vessels

ABSTRACT

A clot retrieval device comprises an elongate shaft  104  and an expandable clot retrieval element  2101  on the shaft, the clot retrieval element comprising a framework formed from a substrate material such as Nitinol and having a plurality of struts  2105  and crowns  2102 , at least some of the struts  2105  comprises at least one widened portion  2104  of the substrate material to provide enhanced radiopacity. The framework is coated with a radiopaque material such as gold. The device is rendered radiopaque with reduced damping effects.

FIELD OF THE INVENTION

This invention relates to devices intended for removing acute blockagesfrom blood vessels. The invention especially relates to means ofrendering such devices visible under x-ray or fluoroscopy. Acuteobstructions may include clot, misplaced devices, migrated devices,large emboli and the like. Thromboembolism occurs when part or all of athrombus breaks away from the blood vessel wall. This clot (now calledan embolus) is then carried in the direction of blood flow. An ischemicstroke may result if the clot lodges in the cerebral vasculature. Apulmonary embolism may result if the clot originates in the venoussystem or in the right side of the heart and lodges in a pulmonaryartery or branch thereof. Clots may also develop and block vesselslocally without being released in the form of an embolus—this mechanismis common in the formation of coronary blockages. The invention isparticularly suited to removing clot from cerebral arteries in patientssuffering acute ischemic stroke (AIS), from coronary native or graftvessels in patients suffering from myocardial infarction (MI), and frompulmonary arteries in patients suffering from pulmonary embolism (PE)and from other peripheral arterial and venous vessels in which clot iscausing an occlusion.

BACKGROUND

Clot retrieval devices comprising a self-expanding Nitinol stent-likemember disposed at the end of a long shaft are commonly used to removeclot from blood vessels, particularly from patients suffering from acuteischemic stroke. These devices are typically provided with small markerbands at either end of the self-expanding member which help to indicatethe device's position. It would be very beneficial to a physician to beable to see the full expandable body of such a device under fluoroscopy,and thus receive visual information on the device's condition as ratherthan simply its position. Clot retrieval procedures are conducted underan x-ray field in order to allow the user visualise the anatomy and at aminimum the device position during a procedure. It is desirable, andenhances the user experience to be able to visualise the device state aswell as position structure during a procedure, for example if the deviceis in an expanded configuration or a collapsed configuration. This meansthat the radiopaque sections must move closer to the device axis in acollapsed configuration and further from a device axis in an expandedconfiguration. It is generally desirable to make interventional devicessuch as clot retrieval devices more flexible and lower profile toimprove deliverability in interventional procedures. This may beachieved by reducing the dimensions for device features, and the levelof contrast seen under x-ray is generally reduced as the devicedimensions are reduced. Radiopaque materials generally comprise noblemetals such as gold, tantalum, tungsten, platinum, iridium and the like,and generally have poor elastic recovery from a strained condition andare therefore not optimal material for devices, particularly for theregions of these devices undergoing high strain in moving from acollapsed to an expanded state and vice versa. Radiopaque materials maybe added through coating a structure comprising a highly recoverableelastic material such as Nitinol, but coating the entire structure has adampening effect that inhibits device performance.

This invention overcomes limitations associated with the dampeningeffect of adding radiopaque material to an expandable clot retrievaldevice, while making the structure sufficiently radiopaque to allow fullvisualisation of the device condition as well as position.

STATEMENT OF THE INVENTION

Various devices and method are described in our PCT/IE2012/000011 whichwas published under the number WO2012/120490A. This PCT applicationclaims the benefit of U.S. Provisional 61/450,810, filed Mar. 9, 2011and U.S. Provisional 61/552,130 filed Oct. 27, 2011. The correspondingU.S. National stage is U.S. application Ser. No. 13/823,060 filed onMar. 13, 2013. The entire contents of all of the above-listedapplications are herein incorporated by reference.

This invention is particularly applicable to clot retrieval devicescomprising expandable bodies made from a metallic framework. Such aframework might be a Nitinol framework of interconnected struts, formedby laser (or otherwise) cutting a tube or sheet of material, and maythus comprise a structure with a pattern of strut features and connectorfeatures. In some embodiments the clot retrieval device may comprise aninner expandable member and an outer expandable member, which may definea flow lumen through a clot and engage a clot.

In order to go from a collapsed to an expanded configuration, portionsof the device undergo recoverable deformation and varying levels ofstrain. Some portions require a higher level of recoverable strain thanothers in order to work effectively. Where the framework or expandablemember comprises a pattern of strut features and connector features, thestruts typically comprise inflection regions or connection regionsgenerally referred to as crowns, which typically experience higherstrain than the struts or connectors when the device is collapsed orexpanded.

The term detector is generally referred to as the part of the equipmentwhich collects the beam for processing into useful images, and caninclude for example flat panel detectors or image intensifiers. X-raybeams are filtered through an anti-scatter grid during processing. Thisfilters out scattered beams which deflect significantly from thetrajectory of the source beam, and beams less significantly deflectedoff the original trajectory pass through the anti-scatter grid creatingareas of overlap between non-scattered photon beams and scattered photonbeams, referred to herein as shadow areas.

In an embodiment of this invention discrete markers are placed in lowstrain regions of the clot retrieval device members, and high strainregions comprise a super elastic material with little or no radiopaquematerial.

In use, it is desirable to maximise visibility and therefore maximisethe area and volume of radiopaque markers located in the clot retrievaldevice. Increasing the ratio of radiopaque material to Nitinol generallyimproves radiopacity. For the effective operation of the device inmoving between expanded and collapsed configurations, it is desirable tomaintain a ratio of Nitinol to radiopaque material such that strainlevels from an expanded to a collapsed configuration are substantiallyin the elastic region. This creates a conflict of requirements, and thesolutions provided herein overcome this conflict.

Discrete markers placed in close proximity create overlapping shadowareas, referred to as intersection zones herein, which give the illusionunder x-ray imaging of a continuous marker thereby providing fullervisual information to the user in an x-ray image.

Various embodiments of the invention are described in more detail below.Within these descriptions various terms for each portion of the devicesmay be interchangeably used. Each of the described embodiments arefollowed by a list of further qualifications (preceded by the word“wherein”) to describe even more detailed versions of the precedingheadline embodiment. It is intended that any of these qualifications maybe combined with any of the headline embodiments, but to maintainclarity and conciseness not all of the possible permutations have beenlisted.

According to the invention there is provided a clot retrieval devicecomprising an elongate shaft and an expandable clot engaging element onthe shaft, the clot engaging element comprising a framework formed froma substrate material and having a plurality of struts and crowns, atleast some of the struts comprising at least one widened portion of thesubstrate material to provide enhanced radiopacity.

In one embodiment the strut comprises a plurality of widened portionswhich are spaced-apart along a length of the strut.

The widened portion of the strut may be at least 50%, optionally atleast 75%, optionally at least 100%, optionally at least 125%,optionally at least 150%, optionally at least 175%, optionally at least200%, optionally at least 300% wider than the regions along the lengthof the strut between the widened portions.

The widened portions may have a length which is less than 100%,optionally less than 75%, optionally less than 50%, optionally less than25% of the length of the regions of the strut between the widenedportions.

The length of the regions of the strut between the widened portions maybe greater than 300%, optionally greater than 400%, optionally greaterthan 500%, optionally greater than 600%, optionally greater than 700%,optionally greater than 800%, optionally greater than 900% of the widthof the strut.

In one embodiment the clot engaging element is cut from a tube ofuniform thickness.

In one embodiment wherein at least a portion of the framework is coatedwith a radiopaque material.

In one embodiment the substrate material is a superelastic material suchas Nitinol or other super or pseudo elastic metallic alloy.

In one case the coating material is Gold, Tantalum, Tungsten, Platinumor an alloy of one of these elements or other dense element or alloycontaining one or more radiodense elements.

In one embodiment the coating material comprises a polymer or adhesivefilled with a dense or high atomic number material such as BariumSulphate, Bismuth SubCarbonate, Barium OxyChloride, Gold, Tungsten,Platinum or Tantalum.

In one case the coating material is applied using an electroplatingprocess, a dipping process, a plasma deposition process, anelectrostatic process, a dip or spray coating process, a sputteringprocess, a soldering process, a cladding process or a drawing process.

The substrate material may have a density of less than 10 g/cm³, lessthan 8 g/cm³.

The coating material may have a density of more than 10 g/cm³, more than15 g/cm³, more than 18 g/cm³.

One embodiment of a device of this invention comprises a clot retrievaldevice comprising an elongate shaft and an expandable section, theexpandable section comprising a framework of interconnected strutelements, the connection region between adjacent strut elementscomprising crown elements, said framework formed from a substratematerial, at least a portion of a plurality of said strut elementscoated with a coating material, and at least a portion of a plurality ofsaid crown elements not coated with said coating material.

The substrate material may have a density of less than 10 g/cm³, lessthan 8 g/cm³.

The coating material may have a density of more than 10 g/cm³, more than15 g/cm³, more than 18 g/cm³.

In one embodiment the substrate material is a superelastic material suchas Nitinol or other super or pseudo elastic metallic alloy.

In one case the coating material is Gold, Tantalum, Tungsten, Platinumor an alloy of one of these elements or other dense element or alloycontaining one or more radiodense elements.

In one embodiment the coating material comprises a polymer or adhesivefilled with a dense or high atomic number material such as BariumSulphate, Bismuth SubCarbonate, Barium OxyChloride, Gold, Tungsten,Platinum or Tantalum.

In one case the coating material is applied using an electroplatingprocess, a dipping process, a plasma deposition process, anelectrostatic process, a dip or spray coating process, a sputteringprocess, a soldering process, a cladding process or a drawing process.

Another aspect of this invention comprises a method of manufacturing theexpandable body of a clot retrieval device, the expandable bodycomprising a substrate material and a coating material, the methodcomprising:

-   -   a first step of applying the coating material to the substrate        material,    -   a second step of removing at least a portion of said coating        material from at least one area of said substrate material,    -   and a third step of cutting away regions of both coating and        substrate material to form an interconnected pattern of coated        and uncoated regions.

In one embodiment the first step comprises an electroplating process, adipping process, a plasma deposition process, an electrostatic process,a dip or spray coating process, a sputtering process, a solderingprocess, a cladding process or a drawing process.

In one case the second step comprises a grinding process, a polishingprocess, a buffing process, an etching process, a laser cutting or laserablation process.

In one embodiment the third step comprises a laser cutting process, awire cutting process, a water jet cutting process, a machining processor an etching process.

In one case the coating material is Gold, Tantalum, Tungsten, Platinumor an alloy of one of these elements or other dense element or alloycontaining one or more radiodense elements.

In one embodiment the coating material comprises a polymer or adhesivefilled with a dense or high atomic number material such as BariumSulphate, Bismuth SubCarbonate, Barium OxyChloride, Gold, Tungsten,Platinum or Tantalum.

In one case the substrate material comprises Nitinol, or an alloy ofNitinol or another super or pseudo elastic alloy.

In one embodiment the interconnected pattern comprises a plurality ofstrut elements and connector elements.

In one case the interconnected pattern of the clot retrieval devicecomprises an expanded state and a collapsed state.

In one embodiment the second step removes at least a portion of thecoating from those areas of the interconnected pattern which experiencethe highest strain in moving from the expanded state to the collapsedstate, and/or from the collapsed state to the expanded state.

In one case the strut elements terminate in crown elements.

In one embodiment the second step removes some or all of the coatingfrom the crown elements.

In one case the second step removes some or all of the coating fromdiscrete sections of the strut elements; in one embodiment thesediscrete sections comprising stripes across the width of the struts.

Another embodiment of a device of this invention comprises a clotretrieval device comprising an elongate shaft and an expandable section,the expandable section formed from a substrate material, at least aportion of the substrate material coated with a first coating materialand at least a portion of the first coating material coated with asecond coating material.

In one case the substrate material is a superelastic material such asNitinol or other super or pseudo elastic metallic alloy.

In one embodiment the first coating material is Gold, Tantalum,Tungsten, Platinum or an alloy of one of these elements or other denseelement or alloy containing one or more radiodense elements.

In one case the first coating material is applied by a plasma depositionprocess, an electrostatic process, a dip or spray coating process, asputtering process, a sputtering process using a cylindrical magnetron,a soldering process, a cladding process or a drawing process.

In one embodiment the first coating material comprises a porous ornon-porous columnar structure.

In one case the first coating material comprises a porous columnarstructure, comprising generally independent columns of the coatingmaterial which extend substantially perpendicularly to the substratesurface.

In one embodiment said columns have a first end and a second end, saidfirst end being adjacent the substrate surface, and the spacing betweenthe second ends of adjacent columns varying with deformation of thesubstrate material/expandable body.

In one case the second ends of the first coating material define anouter surface, and said outer surface is a rough surface.

In one embodiment the second coating material comprises a smoothsurface, and/or a soft surface. In one case the second coating materialis a polymeric material.

In one embodiment the elastic modulus of the second coating material islower than that of the first coating material.

In one case the elastic modulus of the second coating material is lowerthan that of the substrate material.

In one embodiment the elastic modulus of the second coating material isless than 50% of that of the first coating material and/or substratematerial.

In one case the elastic modulus of the second coating material is lessthan 40% of that of the first coating material and/or substratematerial.

In one embodiment the elastic modulus of the second coating material isless than 30% of that of the first coating material and/or substratematerial.

In one case the elastic modulus of the second coating material is lessthan 20% of that of the first coating material and/or substratematerial.

In one embodiment the elastic modulus of the second coating material isless than 10% of that of the first coating material and/or substratematerial.

In one case the second coating material is a hydrophilic material or ahydrogel.

In one embodiment the coefficient of friction of the first coatingmaterial is greater than 0.2, greater than 0.3, greater than 0.4,greater than 0.5.

In one embodiment the coefficient of friction of the second coatingmaterial is less than 0.2, less than 0.15, less than 0.1, less than0.08.

Another embodiment of a device of this invention comprises a clotretrieval device comprising an elongate shaft and an expandable member,the expandable member comprising a proximal section, a body section anda distal section, the body section comprising a metallic framework of afirst (or substrate) material, the metallic framework comprising aplurality of strut elements, said strut elements comprising an outersurface, an inner surface and side wall surfaces, at least one of saidsurfaces comprising a smooth surface and recessed features, at leastsome of said recessed features at least partially filled with a second(coating) material.

In one embodiment the recessed features comprise grooves or slots in thetop surface of a strut element.

In one case the recessed features comprise holes in the top surface of astrut element.

In one embodiment the recessed features comprise holes through a strutelement.

In one case the above holes are circular, or oblong, or square orrectangular.

In one embodiment the recessed features comprise grooves or slots in theside wall of a strut element.

In one case all of the recessed features are filled with the second(coating) material.

In one embodiment at least one of the smooth surfaces are coated withthe second (coating) material.

In one case all of the smooth surfaces are coated with the second(coating) material.

In one embodiment the thickness of coating material in the recessedfeatures is greater than the thickness of coating material on the smoothsurfaces.

Another aspect of this invention comprises a method of manufacturing theexpandable body of a clot retrieval device, the expandable bodycomprising a substrate material and a coating material, the methodcomprising: a first step of removing material from discrete areas of thesubstrate material to form recesses, a second step of applying thecoating material to the substrate material and recesses, and a thirdstep of removing some or all of the coating from the non-recessed areasof the substrate.

Another aspect of this invention comprises a method of applying aradiopaque coating to selective areas of the expandable body of a clotretrieval device, the method involving a masking material andcomprising:

-   -   a first step of applying a masking material to selective areas        of the expandable body,    -   a second step of applying a coating material to the expandable        body,    -   and a third step of removing the masking material from the        expandable body.

Another aspect of this invention comprises a method of manufacturing theexpandable body of a clot retrieval device, the expandable bodycomprising a substrate material and a coating material, the methodinvolving a masking material and comprising:

-   -   a first step of applying the masking material to the substrate        material,    -   a second step of removing at least a portion of said masking        material from at least one area of said substrate material,    -   a third step of cutting away regions of both masking and        substrate material to form an expandable body with masked and        unmasked regions,    -   a fourth step of applying a coating material to the expandable        body, such that the coating material adheres to the unmasked        areas but does not adhere to the masked areas of the expandable        body,    -   and a fifth step of removing the masking material from the        expandable body.

In one embodiment the fourth step comprises an electroplating process, adipping process, a plasma deposition process, an electrostatic process,a dip or spray coating process, a sputtering process, a solderingprocess, a cladding process or a drawing process.

In one case the second step comprises a grinding process, a polishingprocess, a buffing process, an etching process, a laser cutting or laserablation process.

In one case the third step comprises a laser cutting process, a wirecutting process, a water jet cutting process, a machining process or anetching process.

In one embodiment the coating material is Gold, Tantalum, Tungsten,Platinum or an alloy of one of these elements or other dense element oralloy containing one or more radiodense elements.

In one case the coating material comprises a polymer or adhesive filledwith a dense or high atomic number material such as Barium Sulphate,Bismuth SubCarbonate, Barium OxyChloride, Gold, Tungsten, Platinum orTantalum.

In one embodiment the substrate material comprises Nitinol, or an alloyof Nitinol or another super or pseudo elastic alloy.

In one case the expandable body comprises a plurality of strut elementsand connector elements.

In one embodiment the expandable body of the Clot Retrieval devicecomprises an expanded state and a collapsed state.

In one case the third step results in the masking material beingpositioned on those areas of the expandable body which experience thehighest strain in moving from the expanded state to the collapsed state,and/or from the collapsed state to the expanded state.

Another embodiment of a device of this invention comprises a clotretrieval device comprising an expandable body and an elongate shaft,the expandable body comprising a proximal section, a body section and adistal section, the body section comprising a framework of strutelements and at least one fibre assembly, the fibre assembly comprisinga radiodense material.

In one embodiment the distal section comprises a clot capture scaffold.

In one case the clot capture scaffold comprises a net.

In one embodiment the fibre assembly comprises at least one fibre and atleast one floating element, the floating element comprising a radiodensematerial.

In one case the fibre comprises a polymer monofilament, or plurality ofpolymer filaments.

In one embodiment the polymer filament is of LCP, Aramid, PEN, PET, orUHMWPE.

In one case the fibre comprises at least one metallic filament.

In one embodiment the metallic filament is a nitinol wire, or pluralityof such wires.

In one case the metallic filament comprises a nitinol outer layer withan inner core of a radiodense material such as Gold, Platinum, Tantalumor Tungsten.

In one embodiment the floating element is a coil, a tube, or a bead.

In one case the material of the floating element comprises Gold,Tantalum, Tungsten, Platinum or an alloy of one of these elements orother dense element or alloy containing one or more radiodense elements.

In one embodiment the material of the floating element comprises apolymer filled with a dense and/or high atomic number material such asBarium Sulphate, Bismuth SubCarbonate, Barium OxyChloride or Tantalum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a clot retrieval device of the invention;

FIG. 2 a is an isometric view of a portion of a clot retrieval devicecomprising standard material under x-ray imaging;

FIG. 2 b is a representation of an x-ray image of FIG. 2 a;

FIG. 2 c is an isometric view of a portion of another clot retrievaldevice comprising a radiopaque material under x-ray imaging;

FIG. 2 d is a representation of an x-ray image of FIG. 2 c;

FIG. 3 a is an isometric view of a portion of another clot retrievaldevice comprising standard material and radiopaque material under x-rayimaging;

FIG. 3 b is a representation of an x-ray image of FIG. 3 a;

FIG. 4 a is a cross section view of a strut feature of a clot retrievaldevice comprising standard material and radiopaque material;

FIG. 4 b is a representation of an x-ray image of FIG. 4 a;

FIG. 5 schematically represents the resulting x-ray image from twoadjacent shadow zones;

FIG. 6 a is a cross section of a strut feature of a clot retrievaldevice comprising standard material and spaced apart radiopaque materialfeatures;

FIG. 6 b is the a representation of an x-ray image from FIG. 6 a;

FIG. 7 a is an isometric view of a portion of a clot retrieval device;

FIG. 7 b is a developed plan view of the portion of a clot retrievaldevice from FIG. 7 a;

FIG. 8 is a developed plan view of a portion of another clot retrievaldevice;

FIG. 9 is a developed plan view of a portion of another clot retrievaldevice;

FIG. 10 a is a view of a portion of a clot retrieval device;

FIG. 10 b is a detail view of a region of the device shown in FIG. 10 a;

FIG. 10 c is an isometric view of the device shown in FIG. 10 a;

FIG. 11 is an isometric view of a portion of a clot retrieval device;

FIG. 12 is an isometric view of a portion of a clot retrieval device;

FIG. 13 a is an isometric view of a tube used to form a part of a clotretrieval device;

FIG. 13 b is an isometric view of a tube used to form a part of a clotretrieval device;

FIG. 14 is an isometric view of a portion of a clot retrieval device;

FIG. 15 is an isometric view of a portion of a clot retrieval device;

FIG. 16 is an isometric view of a portion of a clot retrieval device;

FIG. 17 a is a side view of an element of a clot retrieval device;

FIG. 17 b is a view of the element shown in FIG. 17 a in bending;

FIG. 18 a is a side view of an element of a clot retrieval device;

FIG. 18 b is a view of the element shown in FIG. 18 a in bending;

FIG. 19 a is a stress-strain curve of a material used in theconstruction of a clot retrieval device;

FIG. 19 b is a stress-strain curve of another material used in theconstruction of a clot retrieval device;

FIG. 19 c is a stress-strain curve of an element of a clot retrievaldevice;

FIG. 19 d is a stress-strain curve of another element of a clotretrieval device;

FIG. 20 a is a side view of part of a clot retrieval device;

FIG. 20 b is a side view of part of a clot retrieval device;

FIG. 20 c is a side view of part of a clot retrieval device;

FIG. 21 a is an isometric view of part of a clot retrieval device;

FIG. 21 b is a detail view of a region of the device of FIG. 21 a;

FIG. 21 c is a section through one embodiment of a part of FIG. 21 a;

FIG. 21 d is a section through another embodiment of a part of FIG. 21a;

FIG. 22 is a view of a portion of a clot retrieval device;

FIG. 23 is an isometric view of part of a clot retrieval device;

FIG. 24 is an isometric view of part of another clot retrieval device;

FIG. 25 is a cross sectional view of a portion of the device of FIG. 24;and

FIGS. 26 to 27 are enlarged views illustrating different profiles ofcorrugations or ribs.

DETAILED DESCRIPTION

Specific embodiments of the present invention are now described indetail with reference to the Figures, wherein identical referencenumbers indicate identical or functionality similar elements. The terms“distal” or “proximal” are used in the following description withrespect to a position or direction relative to the treating physician.“Distal” or “distally” are a position distant from or in a directionaway from the physician. “Proximal” or “proximally” or “proximate” are aposition near or in a direction toward the physician.

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Although the description of the invention is in the contextof treatment of intracranial arteries, the invention may also be used inother body passageways as previously described.

FIG. 1 is an isometric view of a clot retrieval device 100 with an innerexpandable member 101 and outer member 102. In use, inner member 101creates a flow channel through a clot and its freely expanded diameteris less than that of outer member 102. The inner and outer members areconnected at their proximal ends to an elongate shaft 104, whoseproximal end 105 extends outside of the patient in use. A distalfragment capture net 103 may be attached to the distal end of thedevice.

Positional visualization of this device may be provided by a proximalradiopaque coil 109 and distal radiopaque markers 108. Uservisualization of device 100 would be enhanced by providing visualinformation to the user on device expansion in a vessel or clot. Thisinformation may allow the user to visualise the profile of a clot andprovide a fuller map of the luminal space created upon devicedeployment. As the device is withdrawn, the user will see the deviceresponse as it tracks through the anatomy with clot incorporated. It istherefore desirable to add radiopaque materials to outer member 102and/or to inner tubular member 101 to provide the highest qualityinformation to the user. One of the challenges with incorporatingradiopaque material in such a manner is the dampening effect suchmaterials have on superelastic Nitinol. The inventions disclosed in thisdocument facilitate incorporation of radiopaque material and thereforeproduct visualization without compromising the superelastic response ofthe outer member or inner tubular member. It is intended that any of thedesigns and inventions disclosed may be adopted to enhance theradiopacity of a clot retrieval device such as shown in FIG. 1, or anyclot retrieval device comprising an expandable body.

In the embodiment shown the radiopacity of the outer member is enhancedby the presence of radiopaque elements 107, which are attached to theouter member by supporting fibres 106. These fibres may be connected tothe framework of the outer member by a variety of means, includingthreading the fibres through eyelets or attachment features. Radiopaqueelements 107 may comprise tubes, beads or coils of a radiodense materialsuch as Gold, Tungsten, Tantalum, Platinum or alloy containing these orother high atomic number elements. Polymer materials might also beemployed, containing a radiopaque filler such as Barium Sulphate,Bismuth SubCarbonate, Barium OxyChloride or Tantalum.

FIG. 2 a is an isometric view of a portion of a clot retrieval device1001 with strut feature 1002 and crown feature 1007 comprising asuperelastic material such as Nitinol. The portion of the clot retrievaldevice is shown is an expanded configuration. It can be appreciated thatin the collapsed configuration, for clot retrieval device delivery, thestruts 1002 may move to a position adjacent each other. During aninterventional procedure, such as a neurothrombectomy procedure, thepatient anatomy and device location in visualized with the aid of x-rayequipment such as a fluoroscope. Source x-ray beam 1003 originates at aphoton beam source and targets device 1001. Partially scattered x-raybeam 1004 is the photon beam deflected by device 1001 which passes todetector 1008. Partially scattered x-ray beam generically refers to aphoton beam which may be absorbed or scattered by a material (e.g.photoelectric absorption or Compton scattering). For materials, such asNitinol that is relatively non-radiopaque relative to the treatmentenvironment, source photon beams 1004 may pass through the devicerelatively uninterrupted, without being absorbed, changing trajectory,or without a significant wavelength change.

FIG. 2 b is a representation of resulting image 1011 captured bydetector 1008 in FIG. 2 a. Low contrast image 1013 represents theoutline of device 1012 under x-ray. Device 1012 may not be visible orbarely visible if it comprises standard material such as Nitinol and/orif device strut feature dimensions are small enough to be below adetectable range. This is due to the level of scattering of the x-ray orphoton beam being relatively uninterrupted by device 1012 relative tothe tissue environment in which it is placed.

FIG. 2 c is an isometric view of a portion of a clot retrieval device1021 with strut feature 1022 and crown feature 1027 comprising aradiopaque material, or a superelastic material such as Nitinol fullycovered with radiopaque material through a process such aselectroplating or sputtering. Source x-ray beam 1023 is a source photonbeam between and x-ray source and device 1021. Highly scattered x-raybeam 1025 is the photon beam between device 1001 and detector 1008. Asan source x-ray beam 1023 passes through radiopaque materials, such asnoble metals such as gold, platinum, and the like, the level ofscattering of a beam is relatively much greater than the level ofscattering of either an adjacent non-radiopaque device comprisingNitinol or relative to the treatment environment where source x-raybeams 1023 pass through relatively uninterrupted.

FIG. 2 d is a representation of resulting image 1031 captured bydetector 1028 in FIG. 2 c. High contrast image 1034 represents theoutline of device 1032 under x-ray. Device 1032 is highly visible as itcomprises a radiopaque material or material combination such as Nitinolcoated with a radiopaque material. This is due to the difference highlevel of scattering of the x-ray or photon beam, highly uninterrupted bydevice 1032 relative to the tissue environment in which it is placed.

FIG. 3 a is an isometric view of a portion of a clot retrieval device1041 with strut feature 1042 and crown feature 1047. The devicestructure substantially comprises superelastic Nitinol material,especially at crown feature 1047 where a high level of elastic recoveryis desirable for effective device operation. Discrete radiopaque marker1045 is located on strut feature 1042 as an example of a location on astructural feature of the device which deflects less and requires lesselastic recovery than other features of the device, for example crownfeature 1047. Several embodiments of devices incorporating discreteradiopaque marker 1045 are disclosed later. Source x-ray beam 1043 isused to image device 1041 and in this example a mixture of highlyscattered x-ray beam 1046 and partially scattered x-ray beam 1044 reachdetector 1048.

FIG. 3 b is a representation of x-ray image 1051 of device 1052 capturedby detector 1048 (FIG. 3 a). Low contrast image 1053 represents areas ofdevice 1041 in FIG. 3 a comprising superelastic materials such asNitinol and high contrast image 1054 represents the location of discreteradiopaque marker 1045 in FIG. 3 a which interrupts the path of x-raysource beam 1043. Device 1052 is partially visible to the user as itcomprises sections of a radiopaque material and non-radiopaque material.This is due to the difference level of scattering of the x-ray or photonbeam, highly uninterrupted by discrete radiopaque marker 1045 relativeto the tissue environment and strut feature 1042 and crown feature 1047comprising superelastic material such as Nitinol which has a partiallyscattered x-ray beam.

FIG. 4 a and FIG. 4 b further represent the scattering of x-ray beamsand interruption of beam patterns as they pass through a medical devicesuch as a clot retrieval device. FIG. 4 a is a cross section view ofclot retrieval device 1061 comprising strut feature 1062 with discreteradiopaque marker 1065. Source x-ray beam 1063 passes through thedevice, and the photon beam reaches x-ray detector 1068 to image device1061. The wavelength and trajectory of partially scattered photon beam1066 passed through strut feature 1062 comprising nitinol materialwithout significant disruption. The wavelength and trajectory of highlyscattered photon beam 1066 passed through discrete radiopaque marker1065 is significantly changed or absorbed by said discrete radiopaquemarker.

FIG. 4 b is an illustration of x-ray image 1071 with low contrast image1074, high contrast image 1073, and shadow zone 1075. Shadow zone 1075in FIG. 4 b occurs as a result of a mixture of partially scatteredphoton beams 1064 and highly scattered photon beams 1066 reaching thesame area of detector 1068 in FIG. 4 a.

FIG. 5 is a graphical representation of an x-ray image resulting from oftwo adjacent shadow zones 1085 combining to create an intersection zone1086.

FIG. 6 a is a cross section view of a portion of a clot retrieval device1091 with strut feature 1092 and a plurality of discrete radiopaquemarkers 1095. The device structure substantially comprises superelasticNitinol material, especially strut feature 1092 and especially areaswhere a high level of elastic recovery is desirable for effective deviceoperation such as crown features not shown in this drawing. A pluralityof discrete radiopaque markers 1095 are located on strut feature 1092 asan example of a location on a structural feature of the device whichdeflects less and requires less elastic recovery than other features ofthe device. Source x-ray beam 1093 is used to image device 1091 and inthis example a mixture of highly scattered x-ray beams 1096 andpartially scattered x-ray beam 1094 reach detector 1098 after filtrationthrough an anti-scatter grid.

FIG. 6 b is a representation of x-ray image 1101 of device 1092 (FIG. 6a) captured by detector 1098 (FIG. 6 a). Low contrast image 1104represents areas of device 1091 in FIG. 6 a comprising superelasticmaterials such as Nitinol and high contrast image 1104 represents thelocation of discrete radiopaque markers 1095 in FIG. 6 a whichinterrupts the path of x-ray source beam 1043. Shadow Zone 1105 in FIG.6 a corresponds with, referring back to FIG. 6 a, a location where amixture of highly scattered x-ray beams 1096 and partially scatteredx-ray beams 1094 reach the same location of x-ray detector 1098.Intersection zone 1106 in FIG. 6 b represents a zone where, referringback to FIG. 6 a, a mixture of highly scattered x-ray beams 1096 andpartially scattered x-ray beams 1094 reach the same location of x-raydetector 1098 in a region where discrete radiopaque markers 1095 arelocated in relatively close proximity. The configuration has theadvantage of creating the illusion for the user of a continuous markerunder x-ray imaging, thereby providing fuller information on thegeometry of the device.

FIG. 7 a and FIG. 7 b are respective isometric and developed plan viewsof a repeating pattern of clot retrieval device 1201, comprising strutfeatures 1202 and crown features 1203. Clot retrieval device has anexpanded configuration as shown in FIGS. 7 a and 7 b and a collapsedconfiguration for delivery. In the collapsed configuration areas of highstrain, preferably high elastic strain, are concentrated at crownfeatures 1203. Force is transmitted to crown features 1203 viastructural strut features 1202. Low strain, preferably low elasticstrain, regions are concentrated in strut features 1202.

FIG. 8 is a developed plan view of a portion of another clot retrievaldevice 1301, comprising strut features 1302 and crown features 1303. Inthis embodiment, discrete elongate radiopaque markers 1304 are locatedin strut features 1302, and undergo low levels of strain as clotretrieval device 1301 moves from a collapsed to an expandedconfiguration. As described previously, radiopaque markers generallycomprise noble metals which have lower yield points and thereforereduced elastic recovery in contrast to a superelastic material such asNitinol.

FIG. 9 is developed plan view of another clot retrieval device 1401comprising crown features 1403, strut features 1402, discrete radiopaquemarkers 1404, and inter-marker strut region 1405. In this embodiment,limitations associated with conflicting requirements of highlyrecoverable elastic strain and incorporating radiopaque features tooptimise visibility are overcome. The location of discrete radiopaquemarkers 1404 in low strain strut features 1402 away from high strainlocation crown features 1403 reduces overall plastic strain and spacingdiscrete radiopaque markers apart in a strut to create inter-markerstrut regions 1405 further reduces accumulated plastic strain tooptimise device operation, particularly in moving from a collapsedconfiguration to an expanded configuration and transmission of force byclot retrieval device 1401 in a radial direction, which is desirable foreffective clot retrieval. Referring back to FIGS. 6 a and 6 b, it willbe appreciated that spacing marker bands apart will provide high qualityvisual information to the user due as high contrast regions are createdboth from radiopaque markers and from combined shadow zones whereradiopaque markers are located adjacent each other.

FIG. 10 a is a sectioned plan view of a portion of partially coated clotretrieval device 1501 having crown feature 1510, uncoated strut feature1516, and partially coated strut feature 1511 partially covered in aradiopaque coating 1515. The strut and crown features may comprise ahighly elastic material such as Nitinol, and the radiopaque material maycomprise noble metals such as gold or platinum or the like or a polymermaterial such as polyurethane, pebax, nylon, polyethylene, or the like,filled with radiopaque filler such as tungsten, barium sulphate, bismuthsubcarbonate, bismuth oxychloride or the like or an adhesive filled withradiopaque filler. Strut features and crown features may compriseNitinol material with strut sidewall recess feature 1512. In the exampleshown, strut sidewall recess feature comprises a series of grooves inthe sidewall of the strut. Grooves may be incorporated in a sidewallusing cutting process such as laser cutting or other cutting means ofincorporated through mechanical abrasion, cutting, grinding, orselective chemical etching. Other recess features may be incorporatedsuch as dimples, knurls, or highly roughened surface to achieve anon-planar, textured, or rough surface. The coating can be applied as asingle step (a partially coated device is shown for illustrationpurposes) through a process such as electroplating, sputtering, dipping,spraying, cladding, physical deposition, or other means.

FIG. 10 b is a detailed view of partially coated strut feature 1511showing uncoated groove 1512 for illustration purposes on one side andcoating 1515 on the other side. Device 1501 has strut sidewall recessfeature 1512 and device 1501 is preferentially coated in these areaswith thick coating section 1513 resulting, which is located in alow-strain area for effective operation. The elastic recovery dampeningeffect of coating material 1515 has less impact on low strain strutfeatures. Crown feature 1510 has a thin coating 1514 and is lesspreferentially coated because of its non-recessed, non-textured, orsmooth surface, so potential dampening effect of radiopaque coating isminimised in parts of the clot retrieval device 1501 features requiringmore elastic recovery such as crown feature 1510.

FIG. 10 c is a partially cut isometric view of clot retrieval device1501. The device is shown with coating 1515 partially cut away forillustration purposes. Clot retrieval device 1501 has crown features1510, uncoated strut feature 1516 with strut sidewall recess feature1512 to promote thick coating layer 1513 in on low strain parts of thedevice and thin coating layer 1514 on high strain parts of the device.

FIG. 11 is an isometric view of a repeating cell of clot retrievaldevice 1601 comprising crown feature 1602 and strut feature 1603. Strutfeature 1603 has top surface grooves 1604 to promote preferentialradiopaque coating adherence now on the top surface in a similar mannerto preferential coating deposition or adherence described previously.

FIG. 12 is an isometric view of a repeating cell of clot retrievaldevice 1701 comprising crown feature 1702 and strut feature 1703. Strutfeature 1703 has top surface dimples 1704 to promote preferentialradiopaque coating adherence on the top surface in a similar manner topreferential coating deposition or adherence described previously.Grooves 1604 or dimples 1704 in FIG. 11 and FIG. 12 respectively may beadded through processing techniques such as laser ablation, lasercutting, mechanical abrasion such as grinding, mechanical deformationprocess such as knurling or indentation and the radiopaque coveringdescribed previously.

FIG. 13 a is an isometric view of tubing 1801 comprising Nitinolmaterial 1803 and radiopaque cladding 1802 comprising a radiopaquematerial such as a gold, platinum, iridium or tantalum. This materialmay be processed by means such as electroplating, sputtering, or amechanical compression process such as crimping or drawing.

FIG. 13 b is an isometric view of tubing 1806 with comprising Nitinolmaterial 1803 and cladding 1302 comprising rings of radiopaque material,with intermittent gaps 1304 between cladding rings 1302. Tubing 1806 maybe manufactured from applying a secondary process to tubing 1801 in FIG.13 a by removing annular sections of radiopaque material through aprocess such as laser ablation, laser cutting, or mechanical removalsuch as grinding or cutting for example on a lathe.

FIG. 14 is an isometric view of clot retrieval device 1901. Clotretrieval device 1901 may be constructed of tubing 1806 as shown in FIG.13. Device 1901 may be made through a series of processing steps whereintubing 1806 is cut to form strut and crown patterns, deburred, expandedand heat treated, and electropolished. Crown features 1903, which areareas requiring high elastic recovery, are located in areas in whichcladding 1902 is absent, and strut feature 1904, which undergoes lessstrain and requiring less elastic recovery, is located in areas wherecladding 1902 remains.

FIG. 15 is an isometric view of clot retrieval device 2001 withradiopaque material free crowns 2003 as in device 1901 of FIG. 14 butthe spacing of cladding rings in device 2001 is such that strut 2004also has clad-free areas 2005 to further promote elastic behaviour ofstrut feature 2004. In transitioning from collapsed configuration toexpanded configuration or vice versa, areas of high strain are locatedat crown feature 2003 and elastic recovery is less of a requirement forstrut features 2004. It may however by desirable in use, particularly ifa device is required to conform to a tortuous vessel such in use, forstrut feature 2004 to deflect in bending and recover elastically. Device2001 with radiopaque-material-free areas 2005 has the advantage offacilitating more recoverable strain. Devices 2001 and 1901 may bemanufactured from clad tubing 1806 and cutting a pattern whereby crownfeatures and strut features are located in clad-free and clad areasrespectively, they may also be constructed from tubing 1801 and claddingremoved during or subsequent to the laser cutting process.

FIG. 16 is an isometric view of clot retrieval device 2101 comprisingcrown features 2102 and strut features 2105. In this case the clotengaging framework is formed for example by laser cutting from a tube ofuniform wall thickness. Strut 2105 comprises widened strut sections 2104and regular strut sections 2103, which respectively provide enhancedradiopacity and flexibility. Radiopacity of device 2101 is enhanced bythe addition of widened strut sections 2104 in strut feature 2105. Theincreased material volume in the widened strut section 2104 blocksx-ray/photon beams in contrast to crown feature 2102 and regular strutsection 2013 without compromising device flexibility performance.

A particular advantage of this design is that effective radiopacity maybe achieved through the addition of a much lower volume of radiopaquematerial than would otherwise be possible. For example, if anendovascular medical device comprised a Nitinol strut of width andthickness of between 50 and 100 microns approximately, such a strutwould typically be very difficult for a physician to see underfluoroscopy. If portions of such a strut were made wider as per sections2104 of FIG. 16, these widened sections would create a greater surfacearea and might somewhat improve visibility under fluoroscopy. If such astrut with widened sections were coated with a radiopaque material (suchas any of those previously mentioned) it could be rendered highlyvisible under fluoroscopy, and because of the greater surface area ofthe widened regions 2104, a lesser thickness of radiopaque coating wouldbe needed to make such a device radiopaque than would be the case if thewidened sections were absent. Thus a device with such widened strutfeatures can be rendered radiopaque with significantly reduced adversedamping effects. The width of the widened sections will directly affectthe resultant radiopacity of the device, and will ideally be greaterthan 150 microns, and more preferably greater than 200 microns. Thus thewidth of the widened sections will typically be greater than 1.5 timesthat of the strut, and preferably 2 or more times that of the strut. Inorder to minimize impact on the wrapped profile of the device thewidened areas will be staggered on adjacent struts, so that they do notcontact each other when the device is in the collapsed state. The shapeof the widened sections may (in plan view) be circular or elliptical orsquare or rectangular or any shape that serves to increase the surfaceof the strut and hence increase visibility. In one embodiment a hole oreyelet is provided within the widened area, which could serve as anattachment point for another component, or simply serve to remove massfrom the device and enhance flexibility. Any number of widened areas maybe provided on a device or strut, but ideally two or more widened areasare provided so that visual information is provided to the observer ofthe condition as well as the position of the strut in question.

The widened portion of the strut may be at least 50%, optionally atleast 75%, optionally at least 100%, optionally at least 125%,optionally at least 150%, optionally at least 175%, optionally at least200%, optionally at least 300% wider than the regions along the lengthof the strut between the widened portions.

The widened portions may have a length which is less than 100%,optionally less than 75%, optionally less than 50%, optionally less than25% of the length of the regions of the strut between the widenedportions.

The length of the regions of the strut between the widened portions maybe greater than 300%, optionally greater than 400%, optionally greaterthan 500%, optionally greater than 600%, optionally greater than 700%,optionally greater than 800%, optionally greater than 900% of the widthof the strut.

FIG. 17 a is a cross section of a structural element 2204 in anon-strained condition of clot retrieval device 2201 comprising Nitinolmaterial, with radiopaque material coating 2202. Line 2203 represents aline or plane within structural element 2204 away from the neutral axisof bending.

FIG. 17 b is a cross section of structural element 2204 in a strainedconfiguration through a bending load.

FIG. 18 a is a cross section of structural element 2304 of clotretrieval device 2301 comprising superelastic material such as Nitinoland discontinuous radiopaque coating 2302. Line 2303 is a reference lineclose to device surface away from the neutral axis of structural element2304. In FIG. 18 b, structural element 2304 is shown in the deformed orbent configuration with line 2303, which is between the neutral axis andthe outer surface, representing a line or plane of constant strain.Discontinuous radiopaque coating 2302 may be deposited through meanssuch as a sputter coating process, growing single crystals on thesurface in a discrete fibre-like micro or nano-structure or columnarstructure. Other means of achieving discontinuous radiopaque coatinginclude micro-laser ablation of layers or mechanical separation such asslicing. One advantage of such a coating structure is that a high strain(or deformation) can be induced in the substrate material without a highstrain being induced in the coating material. This is because thediscrete micro-fibres or micro-columns from which the coating iscomposed have minimal connectivity between each other. Thus the outerends of the micro-fibres or micro-columns simply move further apart whena convex bend is applied to the substrate material as shown in FIG. 18b. A smooth surface may subsequently be achieved on the device bycoating with a polymer coating, such as a layer of Pebax for example, orParylene, or a hydrophilic material and/or a hydrogel.

Deformation, such as the applied bending load shown in FIG. 17 by way ofexample, causes material to deform in tension along line 2203. Formaterials such as Nitinol, the stress-strain or force-deflectiondeformation generally follows a curve shown in FIG. 19 a where materialalong line 2204 starts at point A in and follows the arrows to generatea typical flag-shaped stress-strain curve. Stress or force is shown onthe y-axis and strain or deflection is shown along the x-axis of FIG.19. When an applied load or deflection is removed, for nitinol, the loadis reversed at point R and the material follows the unloading curveshown until it reaches point B. For a perfectly elastic of pseudoelasticmaterial, point A and point B are coincident and there is no residual orplastic strain in the material, and therefore no permanent deformation.

Referring now to FIG. 19 b, a pattern of stress-strain is shown which ismore typical of a radiopaque material such as gold, where loading beginsat point A and the stress-strain behaviour follows the loading patternshown until the load is removed and the strain reduces to point B. Sincepoint A and point B are not coincident, plastic or permanent deformationresults, which is quantified as the distance between point B and pointA. Considering the structural element 2201 comprising material such asNitinol combined with radiopaque material such as Gold, the loading andunloading pattern is illustrated in FIG. 19 c wherein load or strain isapplied, and when the load is removed at point R, the internal materialstress-strain response follows the curve from point R to point B. Thecombined material properties are such that plastic strain, defined bythe distance between B and A along the x-axis, results. In thisconfiguration the plastic strain is less than that of pure radiopaquematerial but more than that of pure Nitinol. The dampening effect ondevice recovery is generally not desirable for effective operation ofclot retrieval device performance.

FIG. 19 d is a stress-strain curve of structural element 2301 inbending, taking line 2303 as an example, where the device is loaded frompoint A to point R and when the load is removed the device unloads frompoint R to point B. The magnitude of plastic strain is reduced (reduceddistance between point B and A when comparing FIGS. 19 c and 19 d) asthe coating becomes more discontinuous, and approaches zero as thenumber of discontinuities increases.

FIG. 20 a is a side view of clot retrieval device outer member 2401comprising strut features 2402 and crown features 2403. Radiopaquefilaments 2405 are connected between crown features or strut features toenhance device radiopacity. Radiopaque filaments are located along theouter circumference of clot retrieval device outer member 2401 in orderto enhance fluoroscopic visualisation of the expanded or collapsedconfiguration of the device. The circumferential location of thefilaments may also aid visualisation of device interaction with a clotduring use. The filaments may run parallel to the axis of the device, orin a helical path from crown to crown, crown to strut, or strut to strutin order to maintain clot reception space 2406 for clot retrieval.Radiopaque filaments may comprise single of multiple strands ofradiopaque wire such as tungsten, platinum/iridium or gold, or similarmaterials.

FIG. 20 b is a side view of clot retrieval device outer member 2501comprising strut features 2502 and crown features 2503. Filaments 2505incorporating radiopaque beads 2506 are connected between crown featuresor strut features to enhance device radiopacity. Sequenced radiopaquebeads 2505 along filaments 2505 do not contribute to the mechanicalstiffness of the device or contribute to or detract from radial force inany way, and in a collapsed configuration wrap into inter-strut spacesin a versatile manner. The filaments may run parallel to the axis of thedevice, or in a helical path from crown to crown, crown to strut, orstrut to strut in order to maintain clot reception space 2507 for clotretrieval as in FIG. 20 a. While radiopaque beads are spaced apart tomaintain beaded-filament flexibility, adjacent beads create the illusionof a continuous radiopaque member, providing high quality visualinformation to the user. Filaments may comprise high ultimate tensilestrength monofilament or multifilament polymers such as UHMWPE, Kevlar,aramid, LCP, PEN or wire such as Nitinol and radiopaque beads maycomprise polymer filled with radiopaque filler such as tungsten powder,barium sulphate, of solid radiopaque material such as gold or platinum.

FIG. 20 c is a side view of clot retrieval device outer member 2601comprising strut features 2602 and crown features 2603. Filaments 2605are incorporated in device outer member 2601 in a similar matterdetailed in FIG. 20 b, with radiopaque coils 2608 located on filament2605. Radiopaque coils may comprise wound wire such as platinum/iridiumor platinum/tungsten or similar radiopaque wire wound into a spring-likecoil structure. Filaments 2605 incorporating radiopaque coils 2608maintain flexibility in bending so device performance characteristicssuch as flexibility, trackability, radial force, deliverability, etc.are not compromised.

FIG. 21 a is an isometric view of clot retrieval device outer member2701 comprising strut features 2702 and crown features 2703. An elongateradiopaque thread 2405 is incorporated in the structural elements, i.e.struts or crowns, of clot retrieval device outer member. Elongateradiopaque thread 2704 threads the perimeter of outer member 2704 todefine the outer boundary of device in an axial and circumferentialdirection under fluoroscopic imaging. A plurality of radiopaque threadsmay be incorporated to further define the boundary of the outer member.

FIG. 21 b illustrates a means of incorporating elongate thread 2804 instrut 2802 through eyelet 2805. Elongate radiopaque thread may beincorporated through other means such as surface adhesion.

FIG. 21 c and FIG. 21 d are cross section views of bifilar elongateradiopaque threads 2901 and 3001 respectively incorporated in outermember 2701 in FIG. 21 a. Thread 2904 is a single material radiopaquethread such as platinum/iridium, platinum/tungsten, or gold. Thread 3001in FIG. 21 d comprises Nitinol outer material 3003 with inner radiopaquecore such as a gold core. The coaxial configuration of radiopaque thread3001 part retains the elasticity/elastic recovery, in particular at lowstrains, and has the advantage of contributing to the structuralintegrity of clot retrieval device 2701, for example it may be used toenhance the radial force of the device. The bifilar configuration ofthread 2901 enhances radiopacity by increasing the effective area orvolume of material scattering the x-ray field while maintaining goodflexibility.

FIG. 22 is a plan view of clot retrieval device cell 3101 comprisingstructural strut 3102 and structural crown 3102 with radiopaque markers3106 traversing cell 3101, connected via non-structural struts 3107.Non-structural struts 3107 are connected to structural struts 3102 atconnection crown 3105, and have minimal structural integrity andtherefore minimal contribution to the structural rigidity in bending andin the radial direction. The cell may comprise a Nitinol material withradiopaque markers incorporated in eyelets using a crimping process.

FIG. 23 is an isometric view of clot retrieval device cell 3201comprising crown features 3203 and strut features 3202. A radiopaquefilament 3204 is threaded through side holes 3205 in strut 3202. Sideholes 3205 facilitate incorporation of radiopaque filament ininter-strut space, therefore not adding to the outer or inner profile ofthe device. Radiopaque filament may comprise radiopaque material, orpolymer or wire monofilaments or yarns with radiopaque beads or coilsdescribed previously.

FIG. 24 is an isometric view of a portion of clot retrieval device 3301comprising crown features 3303 and strut features 3302. Strut 3302comprises thickened strut sections 3304 which provide enhancedradiopacity through the additional material volume and surface areaprovided. In one embodiment the device 3301 also compromises aradiopaque coating, which covers some or all of the outer surface of thedevice. This coating may be one of the various coatings previouslydescribed herein. In one preferred embodiment the clot retrieval deviceis made of Nitinol and the radiopaque coating is Gold. In the mostpreferred version of this embodiment the Gold coating is applied by asputter coating or plasma deposition process, rather than by anelectroplating process. A strike layer may be placed between the Goldradiopaque layer and the Nitinol to improve adhesion.

In the embodiment shown the sidewalls 3307 of struts 3302 and crownfeatures 3303 are profiled with a corrugated shape 3305. This corrugatedshape serves to increase the surface area of the device and helps toreduce the damping effect of the radiopaque coating on the recovery ofthe Nitinol device. When device 3301 is wrapped down for delivery, thestruts and crowns deform and bend. As the struts bend the side wallseither elongate or compress depending on whether they are in tension orcompression. The strain induced by this elongation or compression cancause plastic deformation in the radiopaque coating if it is greaterthan the elastic strain limit of the material, which is typically lessthan 1%. However the corrugated surface has the effect of increasing theeffective length of the side wall of the strut and thus reducing theeffective strain on the radiopaque coating, so that the damping effectcan be reduced or eliminated.

FIG. 25 shows one embodiment of a section view through strut 3302 ofFIG. 24. Strut 3302 is comprised of a Nitinol core 3309 and a radiopaquecoating 3308. In this embodiment the top surface 3306 of strut 3302 hasa corrugated profile 3310, providing an additional damping reduction tothat described for the side walls above.

FIGS. 26 and 27 show alternative corrugation profiles 3331 and 3351,which might be adopted in place of corrugations 3305 and 3310 shown inFIGS. 24 and 25.

Modification and additions can be made to the embodiments of theinvention described herein without departing from the scope of theinvention. For example, while the embodiments described herein refer toparticular features, the invention includes embodiments having differentcombinations of features. The invention also includes embodiments thatdo not include all of the specific features described.

The invention is not limited to the embodiments hereinbefore describedwhich may be varied in construction and detail.

1. A clot retrieval device comprising an elongate shaft and anexpandable clot engaging element on the shaft, the clot engaging elementcomprising a framework formed from a substrate material and having aplurality of struts and crowns, at least some of the struts comprisingat least one widened portion of the substrate material to provideenhanced radiopacity.
 2. A clot retrieval device as claimed in claim 1wherein the strut comprises a plurality of widened portions which arespaced-apart along a length of the strut.
 3. A clot retrieval device asclaimed in claim 1 wherein the widened portion of the strut is at least50%, at least 75%, at least 100%, at least 125%, at least 150%, at least175%, at least 200%, at least 300% wider than the regions along thelength of the strut between the widened portions.
 4. A clot retrievaldevice as claimed in claim 1 wherein the widened portions have a lengthwhich is less than 100%, less than 75%, less than 50%, less than 25% ofthe length of the regions of the strut between the widened portions. 5.A clot retrieval device as claimed in claim 1 wherein the length of theregions of the strut between the widened portions is greater than 300%,greater than 400%, greater than 500%, greater than 600%, greater than700%, greater than 800%, greater than 900% of the width of the strut. 6.A clot retrieval device as claimed in claim 1 wherein the clot engagingelement is cut from a tube of uniform thickness.
 7. A clot retrievaldevice as claimed in claim 1 wherein at least a portion of the frameworkis coated with a radiopaque material.
 8. A clot retrieval devicecomprising an elongate shaft and an expandable section, the expandablesection comprising a framework of strut elements and connections betweenthe strut elements, the framework being formed from a substratematerial, wherein at least some of the strut elements have enhancedradiopacity with respect to the radiopacity of the connection betweenthe strut elements.
 9. A clot retrieval device as claimed in claim 8wherein the connections comprise crown elements.
 10. A clot retrievaldevice as claimed in claim 8 comprising a first coating on at leastportion of the strut elements.
 11. A clot retrieval device as claimed inclaim 9 comprising a second coating on at least portion of the crownelements.
 12. A clot retrieval device as claimed in claim 9 to 11comprising a first coating on the strut elements and a second coating onthe crown elements.
 13. A clot retrieval device as claimed in claim 12wherein the first and second coatings are of the same material.
 14. Aclot retrieval device as claimed in claim 12 wherein the first andsecond coatings are of different materials.
 15. A clot retrieval deviceas claimed in claim 12 wherein the thickness of the first coating variesalong a length of a strut element.
 16. A clot retrieval devicecomprising an elongate shaft and an expandable clot engaging elementmounted on the shaft, the clot engaging element having a collapseddelivery configuration and an expanded deployed configuration, the clotengaging element comprising a framework formed from a substrate materialof a shape memory material and having a plurality of struts and crowns,at least some of the struts and crowns being of corrugated profile alongthe length thereof to increase the surface area of the clot engagingelement.
 17. A clot retrieval device as claimed in claim 16 wherein thestruts and crowns comprise a plurality of curved ribs extending alongthe longitudinal length thereof.
 18. A clot retrieval device as claimedin claim 17 wherein the pitch of the ribs is from 10% to 300%, from 10%to 200%, from 10% to 100%, from 20% to 50% of the wall thickness of thestruts.
 19. A clot retrieval device as claimed in claim 17 wherein theribs comprise a bend radius between 5 and 125 microns, between 5 and 100microns, between 5 and 50 microns, between 10 and 30 microns.
 20. A clotretrieval device as claimed in claim 14 wherein at least a portion ofthe framework is coated with a radiopaque material such as gold.
 21. Aclot retrieval device comprising an elongate shaft and an expandablesection, the expandable section comprising a framework of interconnectedstrut elements, the connection region between adjacent strut elementscomprising crown elements, said framework formed from a substratematerial, at least a portion of a plurality of said strut elementscoated with a coating material, and at least a portion of a plurality ofsaid crown elements not coated with said coating material.
 22. A deviceas claimed in claim 1 wherein the substrate material has a density ofless than 10 g/cm³, optionally less than 8 g/cm³.
 23. A device asclaimed in claim 21 wherein the coating material has a density of morethan 10 g/cm³, optionally more than 15 g/cm³, optionally more than 18g/cm³.
 24. A device as claimed in claim 1 wherein the substrate materialis a superelastic material such as Nitinol or other super or pseudoelastic metallic alloy.
 25. A device as claimed in claim 7 wherein thecoating material is Gold, Tantalum, Tungsten, Platinum or an alloy ofone of these elements or other dense element or alloy containing one ormore radiodense elements.
 26. A device as claimed in claim 7 wherein thecoating material comprises a polymer or adhesive filled with a dense orhigh atomic number material such as Barium Sulphate, BismuthSubCarbonate, Barium OxyChloride, Gold, Tungsten, Platinum or Tantalum.27. A device as claimed in claim 7 wherein the coating material isapplied using an electroplating process, a dipping process, a plasmadeposition process, an electrostatic process, a dip or spray coatingprocess, a sputtering process, a soldering process, a cladding processor a drawing process.
 28. A method of manufacturing the expandable bodyof a clot retrieval device, the expandable body comprising a substratematerial and a coating material, the method comprising: a first step ofapplying the coating material to the substrate material, a second stepof removing at least a portion of said coating material from at leastone area of said substrate material, and a third step of cutting awayregions of both coating and substrate material to form an interconnectedpattern of coated and uncoated regions.
 29. A clot retrieval devicecomprising an elongate shaft and an expandable section, the expandablesection formed from a substrate material, at least a portion of thesubstrate material coated with a first coating material and at least aportion of the first coating material coated with a second coatingmaterial.
 30. A clot retrieval device comprising an elongate shaft andan expandable member, the expandable member comprising a proximalsection, a body section and a distal section, the body sectioncomprising a metallic framework of a first (or substrate) material, themetallic framework comprising a plurality of strut elements, said strutelements comprising an outer surface, an inner surface and side wallsurfaces, at least one of said surfaces comprising a smooth surface andrecessed features, at least some of said recessed features at leastpartially filled with a second (coating) material.
 31. A method ofmanufacturing the expandable body of a clot retrieval device, theexpandable body comprising a substrate material and a coating material,the method comprising: a first step of removing material from discreteareas of the substrate material to form recesses, a second step ofapplying the coating material to the substrate material and recesses,and a third step of removing some or all of the coating from thenon-recessed areas of the substrate.
 32. A method of applying aradiopaque coating to selective areas of the expandable body of a clotretrieval device, the method involving a masking material andcomprising: a first step of applying a masking material to selectiveareas of the expandable body, a second step of applying a coatingmaterial to the expandable body, and a third step of removing themasking material from the expandable body.
 33. A method of manufacturingthe expandable body of a clot retrieval device, the expandable bodycomprising a substrate material and a coating material, the methodinvolving a masking material and comprising: a first step of applyingthe masking material to the substrate material, a second step ofremoving at least a portion of said masking material from at least onearea of said substrate material, a third step of cutting away regions ofboth masking and substrate material to form an expandable body withmasked and unmasked regions, a fourth step of applying a coatingmaterial to the expandable body, such that the coating material adheresto the unmasked areas but does not adhere to the masked areas of theexpandable body, and a fifth step of removing the masking material fromthe expandable body.
 34. A clot retrieval device comprising anexpandable body and an elongate shaft, the expandable body comprising aproximal section, a body section and a distal section, the body sectioncomprising a framework of strut elements and at least one fibreassembly, the fibre assembly comprising a radiodense material.